Flip-Chip LED Electrode Structure for Thermal and Optical Performance
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Solution Overview
Problem
The existing flip-chip mounting technology for light emitting devices faces issues with peeling at the interface between the electrode and metallic bump, insufficient bonding area, thermal expansion coefficient differences, and low light extraction efficiency due to heat emission and reflectance characteristics.
Innovation Solution
The proposed solution involves a light emitting device structure with a first and second conductive semiconductor layer, electrodes, and an insulating member, where the electrodes have wider contact areas and are formed with the same material as the first electrodes to ensure better thermal expansion matching, and lateral side electrodes for improved light reflection and heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If flip-chip mounting technology is used with solder bumps and metallic bumps, then high integration is achieved, but peeling occurs at the interface between electrode and metallic bump
Solution Approach 1:
The patent uses a composite electrode structure consisting of a metallic bump (first electrode) and a contact electrode (second electrode) made of different materials. The metallic bump provides mechanical strength and solderability, while the contact electrode provides good electrical conductivity and thermal expansion matching, creating a composite structure that resolves the peeling issue while maintaining high integration
Solution Approach 2:
The patent changes the material parameters of the electrode structure by introducing a contact electrode with specific material properties (copper or copper alloy) that have thermal expansion coefficient matching with the semiconductor chip. This parameter change prevents peeling at the interface while maintaining the flip-chip mounting configuration for high integration
2Ease of manufacture
If conventional electrode structure is used, then manufacturing is simple, but bonding area between solder bump and metallic bump is insufficient
Solution Approach 1:
The patent extends the electrode structure in the horizontal dimension by making the contact electrode wider than the metallic bump. This dimensional change increases the bonding area between the solder bump and the electrode structure, providing sufficient bonding area while maintaining the flip-chip mounting process simplicity
3Use of energy by moving object
If light emitting device chip emits heat, then electrical energy is converted to light, but heat emission degrades electrical characteristic
Solution Approach 1:
The patent introduces a heat dissipation layer as an intermediary between the semiconductor chip and the substrate. This heat dissipation layer acts as a thermal mediator that conducts heat away from the light emitting device chip, allowing continuous electrical to light conversion while preventing heat accumulation that would degrade electrical characteristics
4Illumination intensity
If light is reflected upward from light emitting device chip, then light extraction occurs, but low reflectance index reduces light extraction efficiency
Solution Approach 1:
The patent changes the optical parameter of the device by introducing a heat dissipation layer with high reflectance properties. This parameter change improves light extraction efficiency by reflecting upward-traveling light back into the active layer, increasing the probability of light extraction while maintaining manufacturing simplicity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances the physical and electrical reliability, light extraction efficiency, and heat dissipation characteristics of the light emitting device, addressing the limitations of existing technologies.
Implementation Method 1
light emitted from the light emitting device chip and reflected upward represents a low reflectance index, so that light extraction efficiency may be lowered
Implementation Method 2
the electrical characteristic of the light emitting device may be degraded due to heat emitted from the light emitting device chip
Data Source
AI summary
The embodiment relates to a light emitting device, a method of fabricating the same, a light emitting device package, and a lighting system. According to the embodiment, a light emitting device includes a light emitting structure including a first conductive semiconductor layer, an active layer, a second conductive semiconductor layer, a first electrode electrically connected with the first conductive semiconductor layer, a second electrode electrically connected with the second conductive semiconductor layer, an insulating member provided on the light emitting structure while exposing the first electrode and the second electrode, a third electrode provided on the first electrode, and a fourth electrode provided on the second electrode. The third electrode includes a first part of the third electrode directly making contact with the first electrode and a second part of the third electrode, which is provided on the first part of the third electrode and has a horizontal width wider than the first part of the third electrode, and the fourth electrode includes a first part of the fourth electrode directly making contact with the second electrode and a second part of the fourth electrode, which is provided on the first part of the fourth electrode and has a horizontal width wider than the first part of the fourth electrode. The light extraction efficiency and the heat radiation characteristic may be improved, and the reliability may be improved.